Question

In my application I am converting a NSString to HexString. But I always require a fixed size(16 bytes) hex string e.g. if the length of my hex string is 15 bytes, I want it to be 16 bytes. I know that I can add zeros at the beginning of the hex string, but how to add that because simply adding a “0” is not working while I am converting it back into NSString.

Answer 1

You can try this code….

+ (NSString *) stringToHex:(NSString *)str
{   
 NSUInteger len = [str length];
   unichar *chars = malloc(len * sizeof(unichar));
   [str getCharacters:chars];

  NSMutableString *hexString = [[NSMutableString alloc] init];

    for(NSUInteger i = 0; i &lt len; i++ )
    {
      // [hexString [NSString stringWithFormat:@"%02x", chars[i]]]; //previous input

      [hexString appendFormat:@"%02x", chars[i]]; //EDITED PER COMMENT BELOW
    }
    free(chars);

   return [hexString autorelease];
 }

I hope this will help you.
happy coding.